Shimano RSX front hub....how do I get the dust cap off?
 

I've got to replace/repack the bearings on this Shimano RSX front hub but I cannot seem to get the dust cap off, does it turn or do I just pop it off? Thanks, this is my first time trying this.

Would have been helpful to say how you've tried to get it off thus far. Dustcaps on most Shimano hubs (including RSX) are press-fit into the hub shell. If they're gonna come out, there are special tools to pull evenly on them, but I usually just use a flathead screwdriver to pry one side out first.

Sometimes dustcaps don't want to be removed, and removing them can crack or bend them. If you're having trouble with this, clean the old grease out as best you can and repack without removing the dustcap.

If you end up bending or breaking the dustcap in the process of getting it off, most bike shops have replacements in their small parts bins.

Generally, you're better off not trying to remove the dustcap. It is a little bit harder to clean the hub with the dustcap in place, but trying to remove the dustcap is VERY likely to bend/wreck it, and you can't get a replacement.

Sheldon "If It Ain't Broke" Brown

Okay, thanks guys, good plan, it seems to be fine so far.

Another quick question: I've put the axle back in and I've put the nuts on either side back on and "snugged" up the nuts, not "super-tight", is that right? The wheel turned really crackly when it was super-tight but much nicer when snug.

look around the net for some tightenin' advise. It is more of an are than a science. Sounds like you are on the right track.

Make sure there is not play or wobble once the wheel is in the fork. (grab the wheel and see if it wiggles side to side). if so it is too loose!

The lock nuts have to be pretty tight against the cones. Otherwise your bearing preload adjustment won't hold.

Yup. The locknuts should be very tight against the cones, but the cones shouldn't be extremely tight against the ball bearings.
Also, if this is a quick-release hub, rememeber to leave some play in the bearings when you adjust, as the axle will be compressed when you tighten the quick-release.